Casting steel alloy having great tenacity and wear resistance



United States Patent F 3,144,326 CASTING STEEL ALLOY HAVING GREAT TENACHTY AND WEAR RESISTANCE Rudolf Egli, Turin, Italy, assignor to Inbega AG, Sankt Gallen, Switzerland, a corporation of Switzerland No Drawing. Filed July 31, 1961, Ser. No. 129,201 Claims priority, application Italy Jan. 16, 1957 7 Claims. (Cl. 75-126) The present invention relates to a steel alloy having great tenacity and at the same time great hardness, resistance to wear and heat and which can also be readily cast without the use of special casting methods and which is intended to serve generally for the manufacture of high efficiency tools.

US. patent application 614,524, filled by the same applicant under date of October 8, 1956, discloses as similar alloy the advantages and characteristics of which are obtained primarily by virtue of a high chromium content and by using as alloying elements only predetermined percentages of vanadium and tungsten. More in particular, this alloy should contain 13 to 20% chrominum with a vanadium and tungsten content which together are less than 50% of the chromium content while the tungsten content should be 4 to 6% and the vanadium content 1.1 to 1.5% of the alloy proportions. As to the remainder, the content of carbon should be more than 1%, preferably 1.1 to 1.4% depending on the amount of chromium and vanadium present.

Later tests have shown as disclosed in applicants earlier application, Ser. No. 705,412, filed December 26, 1957, now abandoned, of which the present application is continuation in part, that these percentages of the alloying elements may vary in the following manner without deleterious effects to the alloy and that a certain relationship should exist between the chromium content and the vanadium content in order that a steel alloy of this type may be obtained which represents the optimum for satisfying the requirements made of such an alloy.

It was disclosed in applicants earlier application, Serial No. 705,412, that in such a chrominm-vanadium-tungsten alloy the chromium content may vary between 8 and 25% and the vanadium content between 1 and 6%.

Applicants continued tests have established that it is more advantageous it limits for the chromium and vanadium contents in the alloy in accordance with the invention are held between 13 and 15% for the chromium and between 2% and 4% for the vanadium which is considerably above the limits previously established and it has been found that it is essential to observe these limits.

Accordingly, it is an object of the invention which is to be protected by the present continuation in part application to provide a steel alloy including the alloying elements chromium, vanadium and tungsten with the contents of chromium varying between 13 and 15% and vanadium between 2 and 4% which is primarily distinguished by the feature that the composition thereof should have a vanadium content which corresponds to from 15 to 25 of the chormium content.

The principal alloying components chromium and vanadium fulfill the intended purpose in this alloy, of great wear resistance and high heat resistance (consistency of temper) in association with tenacity, as a result of the known characteristics of both alloy components. In this connection chromium acts as a carbide former and increases the tenacity and the vanadium increases the wear resistance and the consistency of temper (heat resistance) in connection with great hardness and supports the efiFect of the carbide forming alloying element chromium.

It was observed that when the above ratio between chromium and vanadium is maintained, alloys will re- 3,144,326 Patented Aug. .1 1, 1964 sult which when the lower percentage of vanadium to chromium is used permit tempering already at 550 C. and that the tempering temperatures (as Well as consistency of temper and heat resistance) can be increased by following the higher percentage relationships of vanadium to chromium up to 600 C. at the upper percentage of vanadium. In this manner, high heat resistance is obtained on the one hand and on the other hand vanadium guarantees the wear resistance among all known alloy elements in combination with the large chromium content which increases the tenacity.

It was further observed that with an alloy relationship of chromium and vanadium of 13% and 2% respectively, i.e., with a ratio of V:Cr=15% the steel alloy has an extraordinary tenacity, whereas slightly increasing of the chromium content to 15% and of the ratio of VzCr up to 25% results in a somewhat decreased tenacity and an extraordinarily increased wear resistance. Thus it is possible to provide for the desired degree of tenacity and wear resistance respectively according to the actual use.

The alloy is hardenable at 1130 to 1240 C. and may be tempered at 550 C. It is distinguished particularly by by its great toughness as well as great wear resistance,

while at the same time it possesses the advaneageous.

quality primarily desired, of being readily cast.

In accordance with another object of the present invention, an alloy is provided in which the tungsten content is kept below 4% without any apparent harmful efi'ects on the alloy.

The addition of the tungsten is to be considered merely as a means for simplifying the thermal treatment (hardening), for the tests have shown the tungsten content Whether smaller or larger does not affect the desired possibly greater heat resistance (consistency of temper) as might have been expected. It is also possible without any significant eifect to replace one part, e.g., 2025% of the content of tungsten with molybdenum.

The particular content of carbon in any given case is of great importance for the alloy in accordance with the invention. It depends on the ratio of chromium content to the vanadium content and in accordance with a concept of the present invention the carbon content should be between 1.1% and 1.5% while it must be determined from case to case, depending on the existing ratio of the amounts of chromium to vanadium which are present. If the carbon content is once determined for an existing ratio of chromium to vanadium, it can be shown that the proportion of carbon in the alloy in accordance with the present application allows only of very minor tolerances in either direction, because otherwise a suitable hardness cannot be obtained by the thermal treatment under any circumstances.

The research in connection with the subject of the invention has indicated the following alloys as being especially good for the actual use in practice possessing the qualities described (whereby of course the usual casting tolerances are to be taken into consideration):

Cr, V, per- W, per- C,pe1- VcCr, percent cent cent percent cent Tests With steels alloyed in this manner, i.e., cutters for lathes and for milking machines, have obtained results which as compared to those obtained with high tungsten and cobalt steel alloys, not only were equal to the same in preformance and endurance but were even better.

Evidence for this is found in that, for example, with cutters Where unusually high cutting requirements were made without using any coolant and with continuous collection of blue and grayish chips extremely high endurance times were obtained. In contradistinction to all other rapid steels, the steels alloyed according to the present invention show a tendency of increasing the surface hardness, inasmuch as a hard skin is produced on the tools which are made of such steels when they are used.

In addition to the high eificiency achieved with steels alloyed in this manner advantages of the invention reside also in the fact that the high proportions'of rare and expensive precious alloy components (tungsten, cobalt, etc.) normally required in such alloys are reduced to a very small minimum or can even be entirely omitted and furthermore, what may be most important, that these alloys can be cast bythe conventional methods for casting all types of tools and structural parts, while at the same time they can also be readily hardened.

Having now described my invention and the best method and proportions for carrying the same into practice, I do not wish to be limited thereto, but what I desire to protect by Letters Patent of the United States is set forth in the appended claims.

I claim:

1. A steel alloy of high tenacity especially for chip removing stools comprising about 2% to 4% of vanadium, about 2% to 4% of tungsten, about 13% to 15% of chromium and 1.1% to 1.5% of carbon, balance essentially iron, in which the percentages of the chromium content and the vanadium content are so related that the vanadium content is between 15% to 25% of the chromium content.

2. A steel alloy according to claim 1 having carbon contents of 1.11.2% for the vanadium content of 15%, said carbon contents increasing in proportion to the vanadium contents up to 1.41.5% for the vanadium content of 25%.

3. A steel alloy of high tenacity for chip removing tools comprising 13% of chromium, 2% of vanadium, 4% of tungsten and 1.2% of carbon, balance essentially iron.

4. A steel alloy of high tenacity for chip removing tools comprising 14% of chromium, 3.5% of vanadium, 4% of tungsten and 1.4% of carbon, balance essentially iron.

5. A steel alloy of high tenacity for chip removing tools comprising 15% chromium, 3.8% of vanadium, 4% of tungsten and 1.5 of carbon, balance essentially iron.

6. A steel alloy according to claim 1, wherein the tungsten is partially replaced by molybdenum and wherein the total content of tungsten and molybdenum does not exceed 4%.

7. A steel alloy according to claim 6, wherein /5 to /4 of the tungsten is replaced by molybdenum.

References Cited in the file of this patent UNITED STATES PATENTS 1,599,425 McGuire Sept. 14, 1926 1,695,916 Comstock Dec. 18, 1928 FOREIGN PATENTS 346,231 Switzerland June 30, 1960 

1. A STEEL ALLOY OF HIGH ENACITY ESPECIALLY FOR CHIP REMOVING STOOLS COMPRISING ABOUT 2% TO 4% OF VANADIUM, ABOUT 2% TO 4% OF TUNGSTEN, ABOUT 13% TO 15% OF CHROMIUM AND 1.1% TO 1.5% OF CARBON, BALANCE ESSENTIALLY IRON, IN WHICH THE PERCENTAGES OF THE CHROMIUM CONTENT AND THE VANADIUM CONTENT ARE SO RELATED THAT THE VANDIUM CONTENT IS BETWEEN 15% TO 25% OF THE CHROMIUM CONTENT. 